This invention relates to gripper jaws used with hydraulic vibratory equipment for driving or extracting piling and caissons.
Hydraulic vibratory equipment for driving and piling caissons are known in which the power-driven vibratory head is suspended from a crane and has a pair of power-driven arms that come together and can form a vise-like grip on pilings, caissons and the like.
Once the vibratory head has a vise-like grip on the piling, the vibratory motion of the head aids in either driving the pile inward or extracting a pile from its location. Significant in the success of the driving or extracting work is the vise-like grip that the arms form on the member to either be extracted or driven, usually into an earth formation.
Heretofore, the gripper plates have comprised blocks of metal, some of which have presented knurled surfaces to the piling member or caisson upon which the work was to be performed. While such a gripper jaw may be adequate in the beginning, and may possibly last for a certain period of time, gripper jaws made of metal, and with knurled surfaces, wear quickly when used in such a manner, causing the vibratory head to lose its vise-like grip upon its work member.